The long and short of it: The unpredictability of late deciding voters

We examine the long- and short-campaign forces and their effects on the error variance in models of presidential voting decisions. Using a heteroskedastic probit allows a separate equation for the error variance and thus insight into campaign effects on voter uncertainty. Controlling for political sophistication, partisan strength and ambivalence, the choices of voters deciding later in the campaign are consistently less predictable. This is important because the number of late deciders has increased in recent elections. Furthermore, ambivalence and residing in a battleground state are stronger sources of error variance among late deciders.